Author
Topic: Leuckart reaction (Read 3789 times)

gandalf

Hello it always tries Leuckart with exito but it makes threea attempts that it come failing; somebody know as it is the correct temperature, and the correct conditions of hidrolisis of amide; I warm up around 190 centigrados degrees ah this temperature the reaction reaches ebb tide, five to six hours, the mixture is darkened, it is put brown and black finally; it is too much heat?thank for his answers.

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terbium

180-190°C would probably be about the correct temperature if you were making methamphetamine. I have used this before for methamphetamine, the yields are low, only 30-40% and a lot of black junk is formed. I don't know how well this will work for MDMA, the methylenedioxy ring may be destroyed under these conditions. Some people say that the yields should be higher when the Leuckart is used with formamide to prepare amphetamine but again I wonder about the stability of the methylenedioxy ring when trying to use this method to prepare MDA.

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methlab

Hi! I would like to make some MDA via the leuckart reaction.Therefore i wanted to make some formamide (or ammonium formate), which should also work. I added 25% ammonia to 86% formic acid until ph > 8 to neutralize the acid. Then i setup for vacuum distillation to remove water. When all the water was gone the temp started to rise a little bit, but in between a couple of minutes about 98% of the solution solidified into a white crystal mass, just a little bit of 'something' was left.Can one tell me, if i did something wrong? What should i do to get formamide, or can i use this white crystal mass? If yes, should i dissolve the crystals in something, or will they turn into a liquid when heated again? It sounds a little bit strange to me, to add my lovely ketone to this crystals and then cook everything until...Thanx

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methlab

hi again. sory, i think i didn't search enough, i found a thread called 'Getting formamide from ammonia formate', which made everything clear (hopefully). will continue heating the white mass to about 180, until it stays a liquid, thanx.

Now, this is the formaldehyde version of the leuckart. It's much easier than the normal one. However, it's a very likely thing that if it works for one, it will work for the other.

The leuckart is supposed to work best when the temperature is ramped up slowly and the reaction run for a while.

I recommend performing hydrolysis in-situ, as it will raise yields. Not all the reduced amine forms an N-formyl derivative, and if you isolate the N-formyl derivative, you throw that amine away.

So, read rhodium's page, search the hive a bit, and read those two links. Best of luck to you.

And *nudge nudge* if you do happen to have some extra ketone to play with, well, ning would be very interested to know how well ammonium oxalate amines ketones....suggested molar ratio ketone 1, ammonia 2, oxalic acid dihydrate 6, for starters.

Peace Bee.

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methlab

In a 250ml rbf: 15.5g MDP2P (via buffered performic) was heated with 45g formamide/ammonium formate for 5 hours at around 170C (with liebig on top). Some crystals formed in liebig condenser, but this should not be a problem. Added 75ml H2O and let cool, then added 100ml DCM for extraction. Saved DCM and discarded the greenish/yellowish waterlayer.Distilled of DCM, added 7ml MeOH and 45ml 15% HCl and heated for 2 hours at around 100C. Washed the very dark solution 2x with 50ml DCM, which took up a lot of the dark shit. Now i added 20% NaOH until freebase fell out. (white waterlayer on top, golden freebase at bottom of sepfunnel). Yield of raw mda freebase: around 10g. Extracted waterlayer with 20ml DCM, to get everything out and added to raw freebase. Added an extra 150ml DCM and extracted base into DCM. Stripped of DCM and H2O and vacuumdistilled the rest. At around 145C (water aspirator) 8g of very pure whaterwhite mda freebase came over, which i dissolved in 200ml toluene and gased with the old hcl generator. They are a little bit wet now, so i can not tell you the exact weight, but it should be around 8g. Any comments to improve my knowledge?

greetings & thanx

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ning

Hydrolysis after leuckart is important to yields! And for best yields, do not separate the N-formyl derivative. After heating for awhile, directly add NaOH solution and reflux awhile to hydrolyze in-situ. THEN extract and measure yield.

That's my suggestion.

Also, I remember hearing that for best yields, the leuckart should bee started cool and run long. Think about it.

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armageddon

Also, I remember hearing that for best yields, the leuckart should bee started cool and run long. Think about it.

You mean like slowly going up to 160°C for 5 hours, then VEEERY slowly let climb to 185 over next 4 hours? Using a dean-stark trap prefilled with (ketone-saturated) water (and removing formed H2O continuously like in Antoncho's Leuckart thread)..

...but with at least 2 equivalents NMF/Formamide, and just a tiny amount more conc. formic acid, like 1.1 eq. (instead of formate salts) to achieve acidic conditions (pH 4.5 - do I remember right?)

- Or would you suggest other parameters? (for [n-alkyl]-formamide, not using formate salts!)

(madprosr: "how to turn your leukart to shit", Newbee Forum) (how NOT to do it )

Kinda wierd, but although having spent lots of time with searching, I wasn't able to get to a satifying answer for my question - although the leuckart is probably one of the best-discussed reduction methods at the hive - but regarding correct heatup times, the opinions seem to differ widely...

any more input for me brain cells?

Greetz, A

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DoctorFeelgood

In a 250ml rbf: 15.5g MDP2P (via buffered performic) was heated with 45g formamide/ammonium formate for 5 hours at around 170C (with liebig on top). Some crystals formed in liebig condenser, but this should not be a problem. Added 75ml H2O and let cool, then added 100ml DCM for extraction. Saved DCM and discarded the greenish/yellowish waterlayer.Distilled of DCM, added 7ml MeOH and 45ml 15% HCl and heated for 2 hours at around 100C. Washed the very dark solution 2x with 50ml DCM, which took up a lot of the dark shit.Now i added 20% NaOH until freebase fell out. (white waterlayer on top, golden freebase at bottom of sepfunnel). Yield of raw mda freebase: around 10g. Extracted waterlayer with 20ml DCM, to get everything out and added to raw freebase. Added an extra 150ml DCM and extracted base into DCM. Stripped of DCM and H2O and vacuumdistilled the rest.

Hydrolysis after leuckart is important to yields! And for best yields, do not separate the N-formyl derivative. After heating for awhile, directly add NaOH solution and reflux awhile to hydrolyze in-situ. THEN extract and measure yield.

Can one please clarify the (blue) hint (from ning), which belongs to the (red) synth above ?When should i add the NaOH (after the 5 hours, instead of HCl ?), do i have to use more, because n-formylderivate not separated,...